Galvanic Element Research Articles

Diseases of the mucous membrane and the activity of the galvanic cell in the oral cavity

AIM. The objective of this study is to determine the frequency of detection of active galvanic cells in the oral cavity in the absence and presence of diseases of the oral mucosa, the development of which may be associated with the irritating effect of direct electric current.MATERIALS AND METHODS. Two groups of 50 patients were examined. All patients had at least 2 metal structures in the oral cavity. The first group comprised patients who had no diseases of the mucous membrane, the second group comprised patients with diseases of the oral mucosa. To detect metal structures that could form a galvanic pair, the electrochemical potential of each metal structure was determined and the difference between the potentials obtained was calculated. To determine the activity of a galvanic element formed by galvanic vapors, the hydrogen index of the gingival fluid in the area of these structures was determined.RESULTS AND DISCUSSION. The difference in the electrochemical potentials of metal structures in the studied groups had no statistically significant differences (p > 0.05) and amounted to 129 + 24.7 mV in the first group, to 135 + 19.8 mV in the second. In the first group, 92 % of patients had no significant difference in the hydrogen parameters of gingival fluid near pairs of metal structures (p > 0.05). The hydrogen values were 6.6 + 0.26 at the cathode and 6.9 + 0.35 at the anode. In the second group, in 88 % of patients, when measuring the hydrogen index of the gingival fluid, a high difference in pH values from 0.7 to 1.5 units was found. The values of hydrogen parameters near the cathode were 7.8 + 0.29, and the will of the anode was 6.3 + 0.22 (p < 0.05).CONCLUSION. Measuring the hydrogen parameters of the gingival fluid near metal structures forming a galvanic pair makes it possible to assess the activity of a galvanic cell. In the absence of diseases of the oral mucosa, the detection rate of active galvanic cells was only 8 %, and in diseases of the mucous membrane, active galvanic cells were detected in 88 % of patients.

Development of a Corrosion Model Ofthermal Elenents of Nuclear Power Plants

Nuclear power plants (NPPs) result in accumulation of a significant amount of radioactive products during the process of their storage and the presence of a potential release of radioactive products, in the case of an accident that is a source of potential hazard and risk of radiation impact on the personnel, population and environment in general. The paper shows the microgalvanic corrosion element formed on the inner wall of fuel rods made of Zr + 1%Nb alloy and pellets made of uranium oxides, as well as the outer galvanic element of fuel rods and structural materials of the reactor made of steel of different grades. The hazards caused by corrosion damage and release of hazardous radioactive substances from the reactor based operating area are analyzed. The possibility of predicting the rate of corrosion damage using a mathematical model on the thermodynamic approach is determined and established.

To the Issue of Solid Municipal Waste in the Irkutsk Region

The article presents data on solid municipal waste (SMW) in the Irkutsk region as the main source of pollution of urban and suburban ecosystems. SMW is currently the most massive and dangerous type of waste, which can lead to irreversible consequences. In Russia, very active attention is being paid to the issues of waste collection and recycling in recent years. The objectives, which the authors set themselves, are a detailed analysis of the situation of SMW in the Irkutsk region. Special attention is focused on the location of already existing facilities as well as planned until 2027 ones. Unfortunately, the population of the Irkutsk region is not yet ready for mass separation of garbage according to its origin and recyclability, but a number of measures are proposed to change the situation. Statistical, comparative-geographical, cartographical and the method of comparative analysis and synthesis were used. The paper presents an analysis of the work of regional operators in accordance with the federal project Integrated system of SMW management carried out for the first time. The amount of waste taken to landfills in the Irkutsk region should be reduced by half by 2030 while sorted waste should gain 100 per cent of all garbage thrown away. The study results in the following conclusions: the region is not ready for processing and recycling of certain categories of waste such as glass or galvanic elements. There are simply no recycling facilities for a number of wastes, which leads to uncontrolled emissions and disturbance of the environment (soil, water, and atmospheric air) but the Government of Russia and the Irkutsk Region authorities are actively reforming the system of SMW management.

Corrosion processes at the GGG40 steel–bentonite interface

Abstract. Spheroidal graphite cast iron (GGG40/0.7040) is used as an overpack material for the reference Pollux 10 container, a prototype for the storage of fuel elements in different types of host rocks (Hassel et al., 2019). Corrosion processes are expected to be triggered after some decades, as the contacting bentonite, which is used as fill material, becomes soggy because of the decay of the fission heat generation and the intrusion of pore water as the temperature decreases under the condensation point (King and Padovani, 2011). The distinct electrochemical reactivities of the graphite, ferrite, pearlite, and cementite phases exposed by this material introduce local galvanic elements which influence the topographic evolution of degradation (Spence, 2005). The aim of this work is to elucidate the corrosion dynamics of active and passive areas by following the chemical evolution at the interface of cast iron–bentonite during the first stages after its saturation with geological pore water. Polarization experiments and electrochemical impedance spectroscopy were applied to monitor the corrosion process in a bentonite cell, where GGG40 steel is put into contact with a light compacted Wyoming bentonite slurry 1 : 10 w/w of bentonite to Opalinus Clay pore water (Fig. 1a). Experiments were performed at 30 and 50 ∘C for longer than 3 months. The surface chemistry and morphological changes were investigated by local XPS, SEM-EDX, and TEM (X-ray photoelectron spectroscopy, scanning electron microscopy with energy dispersive X-ray, and transmission electron microscopy, respectively). These experiments were complemented with corrosion studies performed in pore water under different temperatures, hydrostatic pressures, and pH and with and without dissolved oxygen. The polarization curves indicate a constant corrosion rate of GGG40 steel in saturated bentonite after 30 d. SEM micrographs reveal a preferential dissolution of the ferrite phase around the graphite spheres and the ferrite lamellae contained in the pearlitic eutectic. A strong localized dissolution of ferrite along the graphite boundary can be also observed; this is a typical case of crevice corrosion caused by the unhindered access of oxygen to the graphitic cathodic areas (Wang et al., 2022). The surface chemical studies indicate the accumulation of iron oxides, which can be attributed to a hydrated magnetite and the formation of iron silicates (Zhang et al., 2021). TEM pictures of a cross-sectional lamella, including part of graphite sphere, show the formation of a silicate film covering the corroding surface with an irregular adherence (Fig. 1b). The initial relatively high corrosion rate of GGG40 steel can be attributed to the dissolution of the more active ferrite with the formation of poorly passivating iron oxides and silicates. The system is driven towards the dissolution of pearlite at more positive electrode potentials. The bentonite slurry limits the access of oxygen to the graphitic cathodic areas, reducing the corrosion rate by 1 order of magnitude in comparison with that in aerated pore water. A surface enrichment of cementite with superior passive properties and the neutralization of the local elements by approaching the corrosion potential of graphite (Kadowaki et al., 2019) is also expected. Thus, the consumption of oxygen and the transport limitation of the cathodic reaction by bentonite forecast a considerable reduction in the degradation of the container after a sacrificial corrosion phase.

Alternative Electron Sources for Cytochrome P450s Catalytic Cycle: Biosensing and Biosynthetic Application

The functional significance of cytochrome P450s (CYP) enzymes is their ability to catalyze the biotransformation of xenobiotics and endogenous compounds. P450 enzymes catalyze regio- and stereoselective oxidations of C-C and C-H bonds in the presence of oxygen as a cosubstrate. Initiation of cytochrome P450 catalytic cycle needs an electron donor (NADPH, NADH cofactor) in nature or alternative artificial electron donors such as electrodes, peroxides, photo reduction, and construction of enzymatic “galvanic couple”. In our review paper, we described alternative “handmade” electron sources to support cytochrome P450 catalysis. Physical-chemical methods in relation to biomolecules are possible to convert from laboratory to industry and construct P450-bioreactors for practical application. We analyzed electrochemical reactions using modified electrodes as electron donors. Electrode/P450 systems are the most analyzed in terms of the mechanisms underlying P450-catalyzed reactions. Comparative analysis of flat 2D and nanopore 3D electrode modifiers is discussed. Solar-powered photobiocatalysis for CYP systems with photocurrents providing electrons to heme iron of CYP and photoelectrochemical biosensors are also promising alternative light-driven systems. Several examples of artificial “galvanic element” construction using Zn as an electron source for the reduction of Fe3+ ion of heme demonstrated potential application. The characteristics, performance, and potential applications of P450 electrochemical systems are also discussed.

Визначення ступеня небезпеки відходів гальванічних елементів (батарей)

Abstract. In recent decades, the world has faced a new environmental problem ‒ waste electrical and electronic equipment (WEEE). Timely prevention of the formation of WEEE, minimization of their volume, reuse, recycling and recovery of resources ‒ all these issues require urgent appropriate solutions. Aim. Determining the degree of hazard of waste galvanic elements (batteries) and assigning this waste to the category of hazardous or safe according to national norms and rules. Materials and Methods. Waste galvanic cells (batteries) were the object of research. The samples were dissolved in concentrated nitric acid. The solutions were diluted with distilled water, filtered, and then the content of heavy metals was determined according to DSTU ISO 11885:2005 "Water quality. 33 elements were determined by the method of atomic emission spectrometry with inductively coupled plasma" (ISO 11885:1996, IDT) and GOST 30178-96 "Raw materials and food products. Atomic absorption method for determination of toxic elements". Determination of elements was carried out on an optical emission spectrometer with an inductively coupled plasma "SHIMADZU ICPE-9820". Research results. It was established that the content of lead, cadmium, mercury in waste galvanic elements (batteries) does not exceed the established hygienic standards for the soil ("Hygienic regulations of the permissible content of chemical substances in the soil", Order of the Ministry of Health of Ukraine No. 1595 dated 14.07.2020). Mercury: in 25 samples it was detected at a level that is lower than the sensitivity of the method, in two samples it is 2.25 times and 4.2 times less than the Limit Permissible Concentrations (LPC); in four ‒ 27-48.8 times less, in three ‒ 58-91 times less. The LPC of mercury in soil is 2.1 mg/kg. Cadmium: in 1 sample it was detected at a level that is lower than the sensitivity of the method, in 26 samples it is 2-7.5 times less than the LPC; in the 7th ‒ 9-30 times less. The LPC of cadmium in soil is 1.5 mg/kg. Lead: in 13 samples it was detected at a level that is lower than the sensitivity of the method, in 2 samples it was 3 times less than the LPC, in 6 samples it was 12-19.4 times less than the LPC, in 13 samples ‒ in 24-31 times less than LPC. Maximum permissible limit for lead in soil is 32 mg/kg. It was established that the examined waste samples of galvanic elements (batteries) can be classified as safe and processed and disposed of at the appropriate enterprise. Conclusions. The negative effect of WEEE components on the environment and, as a result, on human health is associated with the inevitable risk of their entering environmental objects due to improper handling of waste galvanic elements (batteries). In order to prevent and minimize the risk to the environment and the population, it is necessary to introduce selective sorting of WEEE components at the places of their generation or collection and sending them for processing, as well as to develop sanitary and epidemiological requirements for sorting processes and to carry out an examination of projects and installations for the utilization of such types of waste for compliance these requirements. Key Words: waste electrical and electronic equipment, waste batteries and accumulators, hazard assessment.

On High-Temperature Galvanic Elements of Stand­by Power Supply Sources based on Energy Condensed Systems

Study of ignition, combustion and electrochemical processes occurring in thin multilayer high-temperature galvanic elements derived from low-gas energy condensed systems was carried out. The research results made it possible to design a wide range of multifunctional standby power supply sources with improved performance, differing in application types, initiation modes, activation and operation times, overall dimensions and shape.

A Critical Review of the Science and Engineering of Cathodic Protection of Steel in Soil and Concrete

After a century of history of cathodic protection (CP) of iron and steel, this paper critically reviews the state of the art in the science and engineering and assesses the fitness of CP as an effective technology to tackle the challenges related to infrastructure corrosion. This paper focuses on CP of iron-based alloys embedded in porous media, such as soil or concrete, as these two major applications of CP technology share many similarities. First, the scientific understanding of CP is reviewed and different competing theories are discussed. There is wide agreement that corrosion protection of steel is achieved thanks to a combination of immediate activation polarization and the beneficial changes in electrolyte chemistry that are gradually occurring at the steel surface when a protection current is flowing toward a steel electrode. A major and well-documented technological advantage of these “chemical effects” is that the protective effect of CP is maintained during temporal loss of protection current, e.g., due to survey work related shut-offs or anodic interference. However, the relationships between these chemical concentration changes in the porous medium and the protection current are complex, and, as this review shows, cannot reliably be described with state-of-the-art approaches. Moreover, in this paper, different hypotheses for the mechanism of corrosion protection in heterogeneous situations (galvanic elements), as they are generally occurring in practice, are discussed. It is revealed that understanding the working mechanism of CP in heterogeneous conditions remains a critical scientific challenge. The longstanding debate concerns the question whether CP results mainly in a reduction of number and size of actively corroding areas, or in a reduction of the corrosion rate at the actively corroding sites. Additionally, the literature addressing the interrelation between microbiologically influenced corrosion and CP is here reviewed, and recent progress as well as limitations of the existing literature are highlighted. In a second part, engineering practice and CP protection criteria are reviewed. It is found that the approaches stipulated in international standard are unreliable. This can be traced back to the assessment criteria being empirical and incapable of adequately taking into account the complexity of the underlying processes. Finally, recommendations for future developments are made. Particular opportunities are seen in embracing the progress made in numerical modeling, such as reactive transport modeling in porous media, and considering the interdependence between the involved processes, namely the interdependence between transport processes, chemical reactions, and electrode kinetics.

Влияние технических лигносульфонатов на коррозию сварных швов в водоугольной суспензии

Hydrotransport of coal, iron ore, bauxite and other solid materials is known to be carried out through trunk pipelines. Hydrotransport of coal in the form of highly concentrated coal-water slurries (HCCWS) makes it possible to solve a whole range of problems from environmental ones to those when HCCWS are used as a fuel for energy boilers. The HCCWS combustion efficiency is determined by the concentration of the solid pulp phase and the particle size. The highest HCCWS combustion efficiency is observed when the mass concentration of the solid phase is 60--65 % and the particle size is up to 0.02 sm. In order to achieve stability of these slurries with the solid phase concentration, various additives are used to improve the rheological properties of coal-water slurries. In particular, such plasticizing agents as sodium tripolyphosphate, technical lignosulfonates, carbon-alkaline reagents and others are used. Plasticizing agents are known to change the rheological properties of coal-water slurries but the problems of corrosion activity of plasticizing agents are not well understood, especially with respect to welded joints of pipelines. Welded joints of slurry pipelines can be represented as macro-galvanic couples, in which the weld and base metal are electrodes of a galvanic element. The current magnitude of the macro-galvanic couple can be used to calculate the local corrosion value due to the work of the galvanic element of the base metal and the weld. The paper studies the effect of technical lignosulfonates (TLS) and TLS-based compositions in a coal-water slurry on the local currents of the base metal --- weld macro-galvanic couple made of 09G2S steel. Findings of research show that in the water-coal slurry the maximum inhibitory effect is observed when 0.75 % TLS + 0.25 % K2CrO4 (Na2CO3) is added to the slurry.

Influence of the gas hydrates on the corrosion rate of gas gathering pipelines

The regularities of corrosion degradation of the low carbon ferrite pearlite St 20 (0.2C) steel of gas gathering pipeline under the mutual effect of corrosion environment, mechanical stresses and hydrate formation were determined. A change in corrosion mechanism in chloride media at increasing chloride concentration from 2.5 mol/L to higher concentration was found. The revealed more significant influence of mechanical stress on localized corrosion rate than on uniform corrosion one was associated with the formation of local galvanic elements on the metal surface and intensification of the metal dissolution in the tensile zone due to the weakening of interatomic interaction caused by increase the distance between grains. Fatigue tests of the pipe steel specimens after exposure to gas hydrate showed a significant decrease in durability (by 15 – 25% depending on test environment), the reason of which was obviously associated with increasing of corrosion damaging of the specimen surface as a result of the aggressive action of gas hydrates.

SVET Study of Amines Attack of MnS Inclusions and the Consequences for Pitting and SCC Nucleation

Sulfide inclusions are preferred nucleation sites for the localized corrosion of carbon and stainless steels. Thus, inclusions distribution and composition are important for the occurrence of pitting, crevice and the different forms of stress corrosion cracking. Amines are usually used for the removal of sulfides, with the precipitation of carbamates by the production of environmental friendly fuels with low S contents. On the other hand, amines are also used associated to formation/injection waters simultaneously to CO2 reinjection by the offshore oil production at high pressures, usually under the assumption that it will act as a corrosion inhibitor, as well. In the present work, we show that amines, usually seen as corrosion inhibitors may enhance the attack to sulfide inclusions in unalloyed carbon steels. For this, artificial galvanic elements with carbon steel (AISI 1006) and MnS tablets (Figure 1.a and 1.c), simulating an inclusion, were studied by SVET (scanning vibration electrode technique) (Figure 1.b and1.d) and other techniques to evaluate the influence of amine (1% tetraethylenepentamine-TEPA) on the corrosion in Na2SO4solutions. Carbon steels (e.g. SAE1006) exposed to dilute sulfate solutions show the typical passive behavior with pitting at higher potentials. The amine “TEPA” shifts the pitting potential to higher values, as expected (Fig. 3a). MnS inclusions show the opposite behavior and its dissolution is promoted when TEPA is added in significant concentrations (Fig. 3b). Accordingly, SVET measurements show that the addition of TEPA can invert the galvanic pair formed by Fe-MnS (Fig. 1). At OCP, a synthetic MnS inclusion is attacked progressively by TEPA as Fig.2 shows for different exposure times. This has significant consequences for the initiation of pitting and stress corrosion cracking of steels, as verified by SVET measurements under simultaneous mechanical strain. Figure 1

Investigation of the Equilibrium Germanium-Substituted Wustite with Metal and Spinel Solutions in the Fе-Gе-O System

The phase equilibrium in the Fe-Ge-O system is investigated by measuring EMF of galvanic elements with solid oxygen-conductive electrolytes. The samples for investigation were prepared by the solid phase reaction at 900 °C. The samples were analyzed to determine the total and phase composition. The gross composition of the samples was refined by chemical analysis. The iron content was determined by the standard method of bichromatometric titration, while that of germanium was determined by the photometric method, which is based on measuring the optical density of the colored colloid solution of germanium phenyl fluoronate, which is formed upon the interaction of germanium dioxide with phenylfluorone in the acidic medium. The phase composition was established using X-ray diffractometry and electron probe microanalysis using a DRON-3 diffractometer and a JEOL JSM-6460LV computer controlled scanning (raster) microscope. The experimental function of EMF galvanic elements of temperature is formulated. After processing the obtained data, the equilibrium oxygen pressures over the samples were calculated, the solubility of germanium in iron monoxide (wustite) was determined, the phase composition of the regions bordering the wustite region was established, the isothermal sections of the state diagram of the system were constructed at 1173 and 1273 K in the equilibrium region of the wustite solution with metallic and spinel phases

Magnesium Sulfur Batteries

Demands in energy storage require a significant improvement in the energy density of battery systems. Therefore innovative systems with a substantially higher specific energy and improved cycle life have to be developed. The combination of Magnesium and Sulfur in a galvanic element addresses several advantages, such as natural abundance, operational safety and a high volumetric capacity. However the research so far was hindered because a stable electrolyte for Mg-S-Batteries was missing [1]. Muldoon et. al. developed a stable and reversibly working non-nucleophilic electrolyte based on a recrystallized Mg2+ salt complex [Mg(µ-Cl)3(THF)6][HMDSAlCl3] (HMDS=hexamethyldisilazid) [2]. This crystalline electrolyte salt though could only be obtained in THF, revealing a disadvantageous overcharging and fast capacity fading [2]. A break-through in Mg/S battery performance was obtained by Fichtner et. al. They at first synthesized a one-step routine between [(HMDS)2Mg]=magnesium bis(hexamethyldisilazid) and AlCl3in different ethers, enhancing solvent choice and possibility of neglecting aforementioned disadvantages [3]. Furthermore a magnesium-anode enhances safety of Mg-S-battery, due to the missing tendency of dendrite formation [4]. Safety as well as capacity and scalability of fabrication of a battery are important factors to assess market opportunities of these secondary cells. Therefore we are focusing on a cell design that is "easy-to-fabricate" with a realistic material loading. Based on the multiannual experience in the development of lithium-sulfur batteries, we extend our activities to the field of magnesium sulfur-battery-development. In a first attempt S-C-cathodes with Sulfur content of 50 wt.% and 70 wt.% were evaluated with a 1.2 M Mg2+-salt electrolyte dissolved in a mixture of 2:1 by volume of bis(2-methoxyethyl)ether and an ionic liquid. The influence of the cathode composition was minimal at this early stage of development. Both types of batteries showed a similar discharge capacity of 600 mAh/g(Sulfur) in the first cycle. Furthermore different approaches for a working Mg-graphite-composite-anode are presented. Such composite-anodes were prepared via die-pressing and could only be obtained in specific composition. The obtained charge-discharge profiles showed remarkably well defined plateaus, which have not been obtained elsewhere, jet (see Figure 1). The preparation routine of the composite-anode was found to have the highest impact on the obtained performance.

DEPENDENCE OF ELECTRIC POTENTIAL OF TREES FROM ENVIRONMENTAL CONDITIONS

In this paper we studied the effect of environmental conditions (light, temperature) on the efficiency of electric power generation by galvanic element formed of a pair of metal electrodes placed in the tree and the soil. Electrodes made from iron, stainless steel and copper. Studied trees of different ages Moscow and Kaluga region: birch, linden, oak, larch, pine, spruce. The potential difference between the wood and soil varied between 0.1 and 0.7 V, depending on the wood species and the electrode material. Maximum efficiency of electricity generation in the summer time was achieved at midday on deciduous trees by using electrodes made of iron (wood) and copper (soil). Made the conclusion that the sunlight accelerate the kinetics of redox reactions in the electrolyte xylem with a metal electrode. Higher values of the potential difference in deciduous trees compared to conifers associated with higher values of pH and the dielectric constant in the sap than in turpentine. The results obtained are useful for the construction of electric power trees batteries, by which can be recharged the low power electronic devices.

RENEWABLE CONCENTRATION GALVANIC CELL AND ITS USE FOR OBTAINING HYDROGEN

The paper proposes a new renewable concentration galvanic element, which includes two identical electrode immersed in a solution of different concentrations, wherein one of the electrodes is immersed in the bed of the river at its outflow into the sea or ocean, and the other electrode is immersed in salt water. The resulting direct current is used to produce hydrogen from sea water in the electrolytic cell. Some specific example of the execution flow of the Sulak river into the Caspian sea.

Measuring the thermodynamic properties of saturated solid solutions in the Ag2Te-Bi-Bi2Te3 system by the electromotive force method

The temperature dependence of the electromotive force (EMF) of Ag|AgI|glass Ag2GeS3|D galvanic elements (where Ag, D are galvanic element electrodes, D is equilibrium three-phase alloys in the Ag2Te-Bi-Bi2Te3 system, AgI|glass Ag2GeS3 is a two-layer membrane with purely ionic (Ag+) conductivity) is studied in the range of 490–550 K. Analytical equations are obtained for the temperature dependences of the Gibbs energies of the formation of saturated solid solutions of the Bi14Te6, Bi2Te, BiTe, and Bi2Te phases from elements in the Ag2Te-Bi-Bi2Te3 system. E(T) analytical equations are used to calculate the standardstate thermodynamic functions of saturated solid solutions of the Bi14Te6, Bi2Te, BiTe, and Bi2Te3 phases in the Ag2Te-Bi-Bi2Te3 system.

New antimicrobial contact catalyst killing antibiotic resistant clinical and waterborne pathogens.

Microbial growth on medical and technical devices is a big health issue, particularly when microorganisms aggregate to form biofilms. Moreover, the occurrence of antibiotic-resistant bacteria in the clinical environment is dramatically growing, making treatment of bacterial infections very challenging. In search of an alternative, we studied a novel antimicrobial surface coating based on micro galvanic elements formed by silver and ruthenium with surface catalytic properties. The antimicrobial coating efficiently inhibited the growth of the nosocomial pathogens Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis and Enterococcus faecium as demonstrated by the growth inhibition on agar surface and in biofilms of antibiotic resistant clinical E. faecalis, E. faecium, and S. aureus isolates. It also strongly reduced the growth of Legionella in a drinking water pipeline and of Escherichia coli in urine. We postulate a mode of action of the antimicrobial material, which is independent of the release of silver ions. Thus, the novel antimicrobial coating could represent an alternative to combat microbial growth avoiding the toxic side effects of high levels of silver ions on eukaryotic cells.

On the applicability of the Stern–Geary relationship to determine instantaneous corrosion rates in macro‐cell corrosion

The well‐known Stern–Geary equation was derived on the basis of the theory by Wagner and Traud and relies on the so‐called mixed potential of an electrode subject to uniform corrosion. Nevertheless, it is common practice to apply the linear polarization method to determine instantaneous corrosion rates in situations of galvanic corrosion. In the present work, the applicability of the Stern–Geary equation to galvanic corrosion was in detail discussed both with help of theoretical considerations and experimental measurements. The primary reason why the application of the Stern–Geary equation to galvanic corrosion is fundamentally incorrect is the fact that a well‐defined mixed potential does for galvanic elements not exist. In this work, equations were derived that allow a correct calculation of the corrosion rate for galvanic cells. However, the required variables can, in usual practical situations, not be measured. Application of the Stern–Geary equation to galvanic cells is in the literature claimed (or assumed) to yield adequate results. An explanation for this apparent applicability was identified in the fact that two major errors have a compensating effect so that they tend to cancel each other out. The extent to which this is possible depends strongly on the actual conditions such as the geometry of the galvanic cell as well as on the position of the counter and the reference electrode (RE). Nevertheless, since this apparent applicability is owing to specific conditions rather than a fundamental applicability of the method, further research is clearly needed to characterize these conditions and their limits in detail.

Thermodynamic properties of the intermediate phases of the Ag-Sb-Se system

The emf (ɛ) dependence of C|Ag|AgI|glass Ag2GeS3|D|C galvanic elements on temperature is studied in the range of 470 to 575 K (C represents current electrodes, D denotes equilibrium three-phase alloys of individual Ag-Sb-Se systems, and AgI|glass Ag2GeS3 is a bilayer membrane with purely ionic (Ag+) electroconductivity). Analytical equations ɛ = ɛ(T) are used to calculate the thermodynamic functions of saturated solid solutions of the AgSbSe2, Sb2Se3, and Ag2Se phases of the Ag-Sb-Se system in the standard state.

Investigation into the equilibrium of the wustite and spinel solutions in the Fe-Ge-O system

Equilibrium conditions of the wustite and spinel solutions in the Fe-Ge-O system in temperature range T = 1100–1300 K are investigated by measuring the emf of the galvanic element with solid electrolyte (the emf method). X-ray diffractometry and electron probe microanalysis were used to determine the phase composition. It is established that the iron magnetite and germanate are partially miscible in one another. The isothermal sections of the phase diagram of the Fe-Fe3O4-Fe2GeO4 system at T = 1273 K and 1173 K are constructed.